The invention relates to apparatus for recording an reproducing electroradiographic images. Apparatus of this general type is known, for example, from the article "A Method of Electronic Read-Out of Electrophotographic and Electroradiographic Images" by Korn et al., Journal of Applied Photographic Engineering, Volume 4, No. 4 (Fall 1978) pages 178-182.
The large-surface electrical recording of radiation images is usually accomplished in the following manner: First, more or less as in television recording tubes, the radiation image is projected onto a surface having electrical properties that respond to the image. Thereafter, a uniform, line-by-line scanning takes place, so that a sequence of signals is obtained which can then be processed, stored and reproduced in many ways. In one known method of image conversion a latent charge image is produced in a photoconductive layer. The charge distribution corresponding to this image is then detected as a pulse sequence as the layer is scanned line-by-line by a flying spot. In this "read-out" procedure, however, two interfering side effects occur. Unlike the situation with an electron-beam vidicon (having a surface of about 10 cm.sup.2), there is a parasitic, i.e., unused, surface that is connected in parallel through a metallic contact, when the entire surface is contacted, due to the very large surfaces (about 1200 cm.sup.2), required in this type of system. As a result, there is not only an increase in the stray capacitance parallel to the point that is to be read out and a consequent reduction in the signal voltage, but, due to the dark conductivity of the photoconductor, there is also a surface area-dependent increase in the dynamic reverse current background. An improvement can be achieved in this respect by breaking up the area to be scanned through a subdivision of the contact electrode into strips. This reduces the parallel capacitance, as well as of the parasitic dark currents, which would otherwise cause an undesirable impairment of the S/N ratio. Image readout apparatus that has been improved in this manner is disclosed, for example, in the publication by Korn et al. referred to above. In the device described there, a plurality of electrically conductive strips are arranged in parallel on the surface of a photoconductive layer with each strip connected to a preamplifier and leading to a storage reading device or a reproduction system. Such an arrangement is costly, however, because a separate amplifier must be provided for each strip. Arrangements of this kind are not well suited to produce the resolutions required for the reproduction of diagnostic X-ray images, for example, because the expense of providing multiple amplifiers is too great with the large number of strips that are necessary for avoidance of artefacts.